The present invention relates to a packaging material for liquid chromatography, in particular, to a packing material for organic solvent type high spped gel permeation chromatography (abbreviated as GPC hereinafter) with high separation performance usable for the separation and the analysis of organic oligomer substances or organic polymer substances and a method for the preparation thereof. GPC is one of liquid chromatography wherein the sample is separated and eluted from the column one after another in order of the fraction with larger molecular weight or molecular size utilizing the principle that, when allowing the sample dissolved into the solvent to develop into the column packed with the packing material (abbreviated as gel hereinafter), the fraction with small molecular weight or molecular size permeates into the pores inside the gel resulting in the long retention time in the gel, whereas, on the contrary, the fraction with large molecular weight or molecular size does not permeate inside the gel but passes through outside of the gel.
And, this organic solvent type GPC has been used widely hitherto as a means for the separation and the analysis of high molecular compounds and oligomers placing many sorts of chemical industries such as petroleum chmistry, polymer chemistry, etc. in center. As the gel used for this GPC, styrene-divinylbenzene type copolymer particles are used widely in general since they are best in the point of overall performance.
The shortcoming of GPC up to this time lies in that sufficiently satisfied separation performance is not obtained compared with other liquid chromatography (adsorption and partition chromatography, ion-exchange chromatography, etc.). However, in case of GPC, the optimization to obtain the high separation performance cannot be aimed through the adjustment of elution conditions of mobile phase or the adjustment of adsorption capacity of stationary phase etc. as in cases of other liquid chromatography. Therefore, with GPC, in place of these, the contrivance to produce the high separation performance has been made by means of a method to lengthen the packing column, a method to decrease the flow rate of measurement, a recycle method to pass the substance to be separated through the column repeatedly and the like. However, with all these methods, a problem that the time for measurement is too long is existent. In particular, the requirement to speed up liquid chromatography more is strong recently and this is not exceptional also with organic solvent type GPC. For this reason, the development of excellent organic solvent type GPC which allows the high separation performance to be maintained in high-speed analysis and satisfys also the durability (stability) at the same time is desired strongly. Conventionally, as the method to make the high-speed analysis possible to some extent, there are a method to shorten the length of column and a method to raise the flow rate on measurement. However, in case of the former, though the total theoretical plate number becomes low and the speed up is attained, the separation performance becomes poor inversely. Moreover, in case of the latter, there are such problems as the separation performance becomes poor under the influences of mass transfer rate, diffusion velocity, etc., while there occur the obstructions on the durability of gel and the apparatus because of an increase in the pressure drop in column when the flow rate of measurement becomes high. Forthermore, as one of the methods to raise the separation performance, there is a method to lengthen the column in order to increase the total theoretical plate number. But, with this method, the speed up cannot be attained, through high separation performance is realized.
On the other hand, the preparation methods through the improvement in the pore volume of gel body or the distribution characteristic of pores, for example,
(a) Improvement in the distribution characteristic of pores by enhancing the constitution rate of monovinyl aromatic monomer in whole monomer. PA1 (b) Enlargement in the pore volume by increasing the amount of organic solvent in the mixture of whole monomer with organic solvent. PA1 (c) Increase in the amount of polymerization initiator to an extent more than that used hitherto to whole monomer (for example, Japanese Patent Publication No. 59847/1982). PA1 (d) Enhancement in the polymerization velocity by using the polymerization initiator with short half-life period (for example, Japanese Unexamined Patent Publication No. 84303/1980). PA1 (e) Polymerization method to control the polymerization ratio to 85 to 98% (for example, Japanese Unexamined Patent Publication No. 69051/1980). are proposed. However, all of these are methods to increase the amount of pore volume or fine pore volume of gel body. Therefore, although the high separation performance is attained to some extent, there is a room for the improvement in the points of mechanical strength, high-speed and durability. Further, by the methods disclosed in, for example, Japanese Unexamined Patent Publication No. 60290/1978, Japanese Unexamined Patent Publication No. 15132/1981. Japanese Unexamined Patent Publication No. 82963/1980, etc. the packing density may be increased to an extent not to make the separation performance poor, but there is still a room for the improvement in the separation performance.
Besides, there is a method to make the average particle diameter of gel small. But this method has a shortcoming that, when making the particles fine leaving as they have same separation performance as that hitherto, the pressure drop in the column becomes very high resulting in the insufficiency of the durability of gel and, if the mechanical strength of gel is insufficient, the packing of gel into the column becomes difficult and the reproducibility of packing becomes also poor resulting in that the column with the separation performance corresponding to the particle diameter is difficult to obtain.
Further, as the method to accomplish the improvement in the durability, there is a method to use the gel with large average particle diameter, but, with this method, the separation performance is insufficient. Besides, there are a method to decrease the amount of whole pore volume of gel body and a method to decrease the amount of fine pore volume without decreasing the amount of whole pore volume. However, whatever method described above may be adopted, it is a present status that the high-speed, the high separation performance and the durability (mechanical strength) are difficult to be satisfied sufficiently at the same time until now. The great reason why these various techniques have been attempted many times is due to the fact that the development of the gel for organic solvent type GPC capable of corresponding to the requirements aforementioned sufficiently has not been made up to this time.
Even if, for example, with the conventional gel of styrenedivinylbenzene type copolymer used widely for the organic solvent type GPC in general, the mechanical strength (durability), the high separation performance and the high-speed cannot be satisfied simultaneously, though they are satisfied individually. That is, according to the conventional techniques, the realization of the gel for organic solvent type GPC capable of satisfying the high-speed, the high separation performance and the mechanical strength at the same time was difficult.
Dissolving the problems described above the corresponding to these requirements, the invention has accomplished the gel satisfying three themes aforementioned at the same time and the method for the preparation thereof.